Compact devices for generating pure hydrogen

ABSTRACT

A hydrogen generator comprising a hydrogen membrane reactor, a fuel supply, a reaction fuel supply line, an air supply, an air supply line, a combustion fuel supply line, a tail gas supply line, a combustion by-product line for transporting combustion by-products from the combustion chamber, and a reaction product line. A membrane assembly to be joined to a reactor chamber of a hydrogen generator, which comprises a membrane; and a membrane support comprising a sintered porous metal. A reactor assembly comprising a reaction chamber containing a porous metal substrate, two membrane assemblies, a fuel supply, a reaction fuel supply line, and a tail gas supply line and a reaction product line. Methods associated with the hydrogen generator, membrane assembly and reactor assembly.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The disclosure was partly made with Government support under contractNo. DAAD19-01-C-0002 by the Department of Defense. The Government hascertain rights in the disclosure.

BACKGROUND

This disclosure relates to hydrogen generating reactors and to hydrogenseparation membranes.

DESCRIPTION OF RELATED ART

The growing popularity of portable electronic devices has produced anincreased demand for compact and correspondingly portable electricalpower sources to energize these devices. Developments in robotics andother emerging technology applications are further increasing the demandfor small, independent power sources. At present, storage orrechargeable batteries are typically used to provide independentelectrical power sources for portable devices. However, the amount ofenergy that can be stored in storage or rechargeable batteries isinsufficient to meet the need of certain applications.

Hydrogen/air fuel cells (H/AFCs) have enormous potential as areplacement for batteries. Because they can operate on very energy-densefuels, fuel cell-based power supplies offer high energy-to-weight ratioscompared with even state-of-the-art batteries. Fuel cells are ofparticular interest to the military, where significant efforts are beingmade to reduce the weight of power supplies that soldiers must carry tosupport high-tech, field-portable equipment. There is also considerablepotential for utilizing fuel cell-based power supplies for commercialapplications, particularly for portable applications where small sizeand low weight are desirable.

A common H/AFC is a polymer electrolyte membrane (PEM) fuel cell. PEMfuel cells are constructed of an anode and a cathode separated by apolymer electrolyte membrane. Functionally, fuel cells generateelectricity by reacting hydrogen with oxygen to produce water. Sinceoxygen can typically be obtained from the ambient atmosphere, only asource of hydrogen must be provided to operate a fuel cell. Merelyproviding compressed hydrogen is not always a viable option, because ofthe substantial volume that even a highly compressed gas occupies.Liquid hydrogen, which occupies less volume, is a cryogenic liquid, anda significant amount of energy is required to achieve the extremely lowtemperatures required to liquefy gaseous hydrogen. Furthermore, thereare safety issues involved with the handling and storage of hydrogen inthe compressed gas form or in the liquid form.

One method of producing hydrogen is by processing hydrocarbons such asmethane (natural gas), propane, butane, and liquid fuels such asgasoline, diesel and JP-8 or oxygenates such as methanol. The choice offuel and the choice of the method of processing, such as steamreforming, partial oxidation, and autothermal reforming, depends to alarge extent on the type of service, such as, portable, stationary orautomotive.

Hydrogen can also be produced by cracking ammonia. The product streamfrom the fuel processor when a hydrocarbon fuel is used containshydrogen in addition to unreacted hydrocarbons, other products such asCO, CO₂, and diluents such as nitrogen. In essence, the hydrogenconcentration in the product stream can be in the 40 to 75 volumetricpercent range depending on the type of fuel and the method ofprocessing. Methods such as water gas shift and preferential oxidationare used to reduce the CO concentrations to acceptable levels of no morethan 50 parts per million, but increase the complexity of the system.

Accordingly, it is desirable to develop a method to yield an efficientand low cost supply of pure hydrogen for fuel cells and otherapplications.

SUMMARY OF THE DISCLOSURE

According to a first aspect, a hydrogen generator is disclosed, thehydrogen generator comprises: a hydrogen membrane reactor having areaction chamber and a combustion chamber, a fuel supply, a reactionfuel supply line, an air supply, an air supply line, a combustion fuelsupply line; a tail gas supply line; a combustion by-product line; and areaction product line for transporting hydrogen from the reactionchamber.

In the hydrogen generator, the reaction chamber of the hydrogen membranereactor is in fluid connection with and heat exchange relationship witha combustion chamber, the reaction fuel supply line is for transportingthe fuel from the fuel supply to the reaction chamber; the air supplyline is for transporting oxygen from the air supply to the combustionchamber, the combustion fuel supply line is for transporting fuel fromthe fuel supply to the combustion chamber; the tail gas supply line isfor transporting tail gases from the reaction chamber; the combustionby-product line is for transporting combustion by-products from thecombustion chamber; and the reaction product line for transportinghydrogen from the reaction chamber.

In one embodiment the fuel supply is replaced by a reaction fuel supplyand a combustion fuel supply, the reaction fuel supply line is fortransporting the reaction fuel from the reaction fuel supply to thereaction chamber and the combustion fuel supply line is for transportingcombustion fuel from the combustion fuel supply to the combustionchamber.

According to a second aspect, a hydrogen generator is disclosed, thehydrogen generator comprising: a hydrogen membrane reactor, an endplate, a membrane assembly and a hydrogen plenum.

In the hydrogen generator, the hydrogen membrane reactor comprises aseparation plate and two chambers on either side of the separationplate, one chamber defining a reaction chamber containing a reactioncatalyst coated to a porous metal substrate, and the other chamberdefining a combustion chamber containing a combustion catalyst coated toa porous metal substrate. In the hydrogen generator the end plate is toclose the combustion chamber on the side opposing the separation plate.

In the hydrogen generator, the membrane assembly contains a membrane anda membrane support sub-assembly, to close the reaction chamber on theside opposing the separation plate, wherein a membrane surface not incontact with the support sub-assembly is situated close to the catalystsubstrate but separated from the catalyst substrate. In the hydrogengenerator, the hydrogen plenum is located on the other side of themembrane assembly to provide a plenum for collecting hydrogen.

According to a third aspect a membrane assembly to be joined to areaction chamber of a hydrogen generator having a hydrogen plenum toform a leak tight reactor sub-assembly, is disclosed. The membraneassembly comprises: a membrane; and a membrane support comprising asintered porous metal.

In the membrane assembly, the membrane is sealed between a first surfaceof the membrane support and a frame. In the membrane assembly a secondsurface of the membrane support is connected to the hydrogen plenum.

According to a fourth aspect, a hydrogen generator is disclosed. Thehydrogen generator comprises: a hydrogen membrane reactor, a feedpre-treatment chamber (herein also indicated as pre-reformer), a fuelsupply, a reaction fuel supply line, a feed supply line, an air supply,an air supply line, a combustion fuel supply line, a tail gas supplyline, a combustion by-product line, and a reaction product line.

In the hydrogen generator, the hydrogen membrane reactor comprises areaction chamber and a combustion chamber, the combustion chamber in afluid connection with and a heat exchange relationship with the reactionchamber. In the hydrogen reactor, the feed pre-treatment chamber is in aheat exchange relationship with the combustion chamber and in fluidconnection with the reaction chamber.

In the hydrogen generator, the reaction fuel supply line is fortransporting fuel from the fuel supply to the feed pre-treatmentchamber, the feed supply line is for transporting treated fuel from thepre-treatment chamber to the reaction chamber, the air supply line isfor transporting oxygen from the air supply to the combustion chamber,the combustion fuel supply line is for transporting fuel from the fuelsupply to the combustion chamber, the tail gas supply line is fortransporting tail gases from the reaction chamber, the combustionby-product line is for transporting combustion by-products from thecombustion chamber; and the reaction product line is for transportinghydrogen from the reaction chamber.

According to a fifth aspect a hydrogen generator is disclosed, thehydrogen generator comprising a hydrogen membrane reactor, an end plate,a pre-treatment chamber, a membrane assembly, and a hydrogen plenum.

In the hydrogen generator, the hydrogen membrane reactor comprises aseparation plate and two chambers on either side of the separationplate, one chamber defining a reaction chamber containing a reformingcatalyst coated to a porous metal substrate, and the other chamberdefining a combustion chamber containing a combustion catalyst coated toa porous metal substrate. In the hydrogen generator, the end plate is toclose the combustion chamber on the side opposing the separation plate.

In the hydrogen generator, the pre-treatment chamber is bound by thecombustion chamber on one side and a bottom plate on the other side andcontains a reaction catalyst coated to a porous metal substrate. In thehydrogen generator, the bottom plate contains a winding of metal tubingon an outer surface to facilitate vaporization of water to steam.

In the hydrogen generator, the membrane assembly contains a membrane anda membrane support sub-assembly, to close the reaction chamber on theside opposing the separation plate, wherein a membrane surface not incontact with the support sub-assembly is situated close to the catalystsubstrate but separated from the catalyst substrate.

In the hydrogen generator, the hydrogen plenum is located on the otherside of the membrane assembly to provide a plenum for collectinghydrogen.

According to a sixth aspect, a hydrogen generator is disclosed, thehydrogen generator comprising: a hydrogen membrane reactor, an internalconnector, a fuel supply, a reaction fuel supply line, an air supply, anair supply line, a combustion fuel supply line, a tail gas supply line,a combustion by-product line, and a reaction product line.

In the hydrogen generator, the hydrogen membrane reactor has acombustion chamber that is sandwiched between a first reaction chamberand a second reaction chamber wherein the combustion chamber is in afluid connection with and in a heat exchange relationship with the firstand second reaction chamber. In the hydrogen generator, the internalconnector connects the first and second reaction chamber wherein thefluid exiting the first reaction chamber flows into the second reactionchamber.

In the hydrogen generator, the reaction fuel supply line is fortransporting fuel from the reaction fuel supply to the first reactionchamber, the air supply line is for transporting oxygen from the airsupply to the combustion chamber, the combustion fuel supply line is fortransporting fuel from the fuel supply to the combustion chamber, thetail gas supply line is for transporting tail gases from the secondreaction chamber, the combustion by-product line is for transportingcombustion by-products from the combustion chamber, and the reactionproduct line for transporting hydrogen from the first and secondreaction chamber.

According to a seventh aspect a membrane assembly is disclosed, themembrane assembly comprising a membrane support sub-assembly and amembrane.

In the membrane assembly, the membrane support sub-assembly comprises asintered porous metal sealed to a perforated metal plate, wherein agasket is disposed between a frame and the membrane, the membrane issealed between the first surface of the support sub-assembly and theframe, and the second surface of the support sub-assembly is welded orbrazed to the hydrogen plenum to form the membrane assembly.

According to a eight aspect a reactor sub-assembly is disclosed, thereactor sub-assembly comprising a reaction chamber containing a porousmetal substrate, two membrane assemblies, a fuel supply, a reaction fuelsupply line, a tail gas supply line and a reaction product line.

In the reactor sub-assembly, the reaction chamber with a substrate issandwiched between the two membrane assemblies thereby providing twomembrane surfaces for hydrogen separation. In the reactor sub-assembly,the fuel supply line is for transporting fuel or hydrogen containingfeed to the reaction chamber, the tail gas supply line is fortransporting tail gas from the reaction chamber, and the reactionproduct line is for transporting pure hydrogen out of each membraneassembly.

According to a ninth aspect, a hydrogen generator is disclosed, thehydrogen generator comprising: a hydrogen membrane reactor, a fuelsupply, a reaction fuel supply line, an air supply, an air supply line,an combustion fuel supply line, a tail gas supply line, a combustionby-product line, and a reaction product line.

In the hydrogen generator, the hydrogen membrane reactor has acombustion chamber that is sandwiched between a first reaction chamberand a second reaction chamber wherein the combustion chamber is in afluid connection with and in a heat exchange relationship with the firstand second reaction chambers.

In the hydrogen reactor, the reaction fuel supply line is fortransporting fuel from the fuel supply to the reaction chambers, the airsupply line for transporting oxygen from the oxygen air supply to thecombustion chamber, the combustion fuel supply line for transportingfuel from the fuel supply to the combustion chamber, the tail gas supplyline is for transporting tail gases from the reaction chambers, thecombustion by-product line is for transporting combustion by-productsfrom the combustion chamber; and the reaction product line is fortransporting hydrogen from the reaction chambers.

According to a tenth aspect a reactor sub-assembly is disclosed, thereactor subassembly comprises a reaction chamber and a membraneassembly.

In the reactor sub-assembly the membrane assembly spans a portion of theentire length of the reaction chamber, and a membrane-less section ofthe reaction chamber is disposed at the entry of the reaction chamberand is used for pre-treatment of a fuel to produce hydrogen containinggases that flow into a section of the reaction chamber exposed to themembrane assembly.

According to an eleventh aspect a method to generate hydrogen from areaction fuel is disclosed, the method comprising: providing a hydrogenmembrane reactor having a combustion chamber in fluid connection withand heat exchange relationship with a reaction chamber, providing areaction fuel supply, transporting the reaction fuel from the reactionfuel supply to the reaction chamber through a first supply line;providing an air supply; transporting oxygen from the air supply to thecombustion chamber through an air supply line; providing a combustionfuel supply; transporting the combustion fuel from the combustion fuelsupply to the combustion chamber through a combustion fuel supply line;reacting the combustion fuel supply in the combustion chamber to provideheat and combustion by-products; reacting the reaction fuel supply withwater in the reaction chamber to provide hydrogen and tail gases;transporting the tail gases from the reaction chamber through a tail gassupply line; transporting the combustion by-products from the combustionchamber through a combustion by-product line; and transporting thehydrogen from the reaction chamber through a reaction product line.

According to a twelfth aspect, a method to generate hydrogen from areaction fuel is disclosed, the method comprising: providing a membraneassembly to be joined to a reaction chamber of a hydrogen generatorhaving a hydrogen plenum to form a leak tight reactor sub-assembly, themembrane assembly comprising a membrane and a membrane supportcomprising a sintered porous metal, wherein the membrane is sealedbetween a first surface of the membrane support and a frame, and whereina second surface of the membrane support is connected to the hydrogenplenum.

The method further comprises: reacting the reaction fuel in the reactionchamber to provide a reaction product comprising hydrogen and tailgases; and separating the hydrogen from the tail gases of the reactionproduct through the membrane assembly.

Other features and advantages of the present invention will be set forthin the following description and accompanying drawings, where thepreferred embodiments of the present invention are described and shown.Additional details will become apparent to those skilled in the art uponexamination of the detailed description taken in conjunction with theaccompanying drawings or may be learned by practicing the presentinvention. The advantages of the present invention may be realized andattained by means of the instrumentalities and combinations particularlypointed out in the appendent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary reactor sub assembly.

FIG. 2 illustrates an exemplary double-sided reactor sub assembly.

FIG. 3A illustrates an exploded perspective view of an exemplarymembrane assembly.

FIG. 3B illustrates a compact perspective view of the membrane assemblyof FIG. 3A.

FIG. 4 illustrates an exemplary reactor subassembly containing twomembrane assemblies as shown in FIGS. 3A and 3B.

FIG. 5 illustrates an exemplary plenum-less variant of the reactorsubassembly of FIG. 1.

FIG. 6 illustrates an exemplary support element of the reactorsub-assembly of FIG. 5.

FIG. 7 illustrates an exemplary variant of the plenum-less reactor subassembly of FIG. 5.

FIG. 8 illustrates an exemplary membrane reactor that integrates thereactor sub assembly of FIG. 1 with a combustion chamber.

FIG. 9 illustrates an exemplary membrane reactor that integrates thereactor sub assembly of FIG. 2 with a combustion chamber.

FIG. 10 illustrates an exemplary variant of the membrane reactor of FIG.9 which includes the membrane assembly shown in FIGS. 3A and 3B.

FIG. 11 illustrates an exemplary variant of the membrane reactor of FIG.8 which includes several membrane assemblies as shown in FIGS. 3A and3B.

FIG. 12 illustrates an exemplary “folded” variant of the membranereactor of FIG. 9, which includes an internal connector between the twochambers.

FIG. 13 illustrates an exemplary plenum-less variant of the membranereactor of FIG. 12 which includes two reaction subassemblies as shown inFIG. 5.

FIG. 14 illustrates the plenum-less “folded” membrane reactor of FIG. 13with an integrated feed gas pre-heater.

FIG. 15A illustrates the exploded view of an exemplary gasketed variantof the “folded” membrane reactor of FIG. 13.

FIG. 15B illustrates the compact view of the exemplary “folded” gasketedmembrane reactor of FIG. 15A.

FIG. 16 illustrates a cross-section of the gasketed membrane reactor ofFIGS. 15A and 15B.

FIG. 17 illustrates an exemplary variant of the membrane reactor shownin FIG. 8 including an integrated water vaporizer and feed pre-treatmentchamber.

FIG. 18 illustrates a cross sectional view of the membrane reactor shownin FIG. 17.

FIG. 19 illustrates a cross sectional view of a variant of the membranereactor of FIGS. 17 and 18, wherein the pre-treatment chamber is notseparated from the reaction chamber.

FIG. 20A illustrates an exploded perspective view of an exemplarymembrane assembly including an integrated gasket.

FIG. 20B illustrates a compact perspective view of the membrane assemblyof FIG. 20A.

FIG. 21 illustrates a cross sectional view of the membrane assemblyshown in FIGS. 20A and 20B.

FIG. 22 illustrates a membrane assembly comprising of tubular membraneelements.

FIG. 23 illustrates a membrane reactor consisting of a tubular membraneassembly of FIG. 22.

FIG. 24 shows a schematic representation of the membrane reactor of FIG.8 in an ammonia based hydrogen generator.

FIG. 25 shows a schematic representation of the membrane reactor of FIG.8 in an hydrocarbon based hydrogen generator.

FIG. 26 shows a diagram reporting measurements of the hydrogen flux(sccm/cm²) through the reactor sub assembly of FIG. 1 described inExample 1. On the y-axis the hydrogen flux is reported. On the x-axisthe time of measurements is reported.

FIG. 27 shows a diagram reporting measurements of the hydrogen flux(sccm/cm²) through a variant of the reactor sub assembly of FIG. 1described in Example 2. On the y-axis the hydrogen flux is reported. Onthe x-axis the test time is reported.

FIG. 28 shows a diagram reporting measurements of the pure hydrogenproduction rate (sccm) through the reactor sub assembly of FIG. 5described in Example 3. On the y-axis the production rate is reported.On the x-axis the test time is reported.

FIG. 29 shows a diagram reporting measurements of the flow rate ofammonia through the reactor sub assembly of FIGS. 13 and 14, describedin Example 5. On the y-axis the flow rates are reported. On the x-axisthe test time is reported.

FIG. 30 shows a diagram reporting the heat content of the membranereject stream described in Example 5. On the y-axis the heat content isreported. On the x-axis the test time is reported.

FIG. 31 shows a diagram reporting the flow rate of ammonia and purehydrogen through the reactor sub assembly of FIGS. 15A, 15B, and 16 asdescribed in Example 6. On the y-axis the flow rates are reported. Onthe x-axis the test time is reported.

FIG. 32 shows a diagram reporting measurements of the hydrogenproduction rate (sccm) through the reactor sub assembly of FIG. 8described in Example 7. On the y-axis the production rate is reported.On the x-axis the test time is reported.

FIG. 33 shows a diagram reporting measurements of the pure hydrogenproduction rate (sccm) through the reactor sub assembly of FIG. 8described in Example 8. On the y-axis the production rate is reported.On the x-axis the test time is reported.

FIG. 34 shows a diagram reporting measurements of the pure hydrogenproduction rate (sccm) through the reactor sub assembly of FIGS. 17 and18 described in Example 9. On the y-axis the production rate isreported. On the x-axis the test time is reported.

FIG. 35 shows a diagram reporting measurements of the pure hydrogenproduction rate (sccm) through the reactor sub assembly of FIGS. 17 and18 described in Example 10. On the y-axis the production rate isreported. On the x-axis the test time is reported.

It should be appreciated that for simplicity and clarity ofillustration, elements shown in the Figures may not necessarily beendrawn to scale. For example, the dimensions of some of the elements areexaggerated relative to each other for clarity.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1 shows a sectional view of one embodiment of a membrane reactorsub assembly (10). The membrane reactor subassembly (10) includes areaction chamber (2), a hydrogen exhaust chamber or plenum (4) and amembrane assembly (3) placed between the chamber (2) and the plenum (4).

The reaction chamber (2) contains a catalyst and comprises a reactorentry port (14) and reject port (16). The plenum (4) includes an exitport (18).

The membrane assembly (3) comprises an hydrogen separation membrane inthe form of a membrane foil (8) and a membrane support sub-assemblyincluding a membrane support (6) having perforations (7) and a metalretaining frame (12). In the membrane assembly (3), the membrane foil(8) is supported by the membrane support (6) and is held in place on themembrane support plate (6) using a metal retaining frame (12).

The hydrogen separation membrane in the form of a foil (8) is disposedoff directly over the catalyst containing reaction chamber (2).

The feed enters the reaction chamber (2) through the reactor entry port(14). Hydrogen is generated in the reaction chamber, permeates throughthe membrane foil (8), flows through the perforations (7) in themembrane support plate (6) and into the plenum (4), and exits thereaction chamber through the hydrogen exit port (18). The reactionchamber tail gases that constitute the gas mixture rejected by themembrane, exit through the reject port (16).

The membrane foil (8) is preferably composed of palladium or alloys ofpalladium, and more preferably alloys of palladium and silver containing70 to 80 at.-% palladium. The thickness of the membrane foil (8) ispreferably in the 10 to 30 micron range although foils of otherthicknesses may also be used.

The membrane support sub-assembly comprising the membrane support (6)and the metal retaining frame (12), may also comprise of a sinteredporous metal substrate or a combination of a sintered porous metalsubstrate and a solid metal plate containing perforations or acombination of sintered porous metal substrate housed in a metal frame.The substrate can be formed of metal foam, metal monolith, metal mesh,ceramic foam, and ceramic monolith. Preferably, metals such asaustenitic stainless steels (e.g., grades 303, 304, and 316) or hightemperature nickel based alloys (e.g., Inconel® 600 series) are used tofabricate the metal components incorporated in FIG. 1. The componentscan have a wall thickness of about 2.5 mm. The use of such metalspermits operation at high temperatures (450° C. to 700° C.) which isdesirable for producing hydrogen. Preferably the sintered porous metalsubstrates such as those supplied by Mott Corp. (Farmington, Conn.) orPall Corporation (East Hills, N.Y.) are used to support the thin foilmembranes as these are typically less than 20% of the cost of machiningperforations into solid metal plate stock and provide improved hydrogentransport compared to perforated plates. The sintered porous metal canhave a thickness in the ranges of 1.0 mm to 6.5 mm, and more preferably1.0 mm to 1.5 mm.

The perforated metal plates can have perforations of different sizes andthe sizes of the perforations provide adequate support to the membraneand adequate porous volume for transporting the hydrogen to the hydrogenexhaust chamber. The porosity can range from 5% to 58% preferably from20% to 50%. The perforations are spaced apart preferably of about 2.5mm. The perforated metal plate can have 15% to 50% open volume and thesintered porous metal can be sealed to the perforated metal plate.

The membrane foil (8) may be joined and sealed in between frame (12) andsupport (6) using methods such as brazing, welding (TIG, MIG, electronbeam, laser), or diffusion bonding. More preferably, the foil membraneis joined by brazing as practiced by Omley Industries (Grants Pass,Oreg.) and American Brazing (Willoughby, Ohio). A preferred alloy forthe brazing process is 82% gold/18% nickel such as the Nioro® alloysupplied by Wesgo, Inc. (Belmont, Calif.) which is typically used inhigh performance aerospace applications. The form of the braze ispreferably an extrudable paste but may also be in foil, flexibraze,wire, or powder form. Brazing is preferably done in a vacuum furnacewith a peak temperature of 960° C. with a ramp rate of 200° C. per hour.During the braze process, a dead weight is applied to the retainingframe to maintain contact between the foil and the support and toprovide a leak tight seal around the perimeter of the foil. The sealbetween the foil and the support may also be achieved without the use ofa metal frame.

For example, a graphite fixture or other material resistant to brazingmay be used to apply pressure during the braze process and then beremoved. In the subsequent figures, the frame may not be shown in themembrane assembly, but it should be understood that the metal frame thatmay or may not be used during brazing, and if used exists only in avestigial manner in the membrane assembly. That is, the frame does notserve any purpose once the membrane assembly is sealed to a reactionchamber to form the reactor sub assembly. A concern during brazing whenusing a perforated plate or a porous metal as a support, is wicking ofthe braze alloy into the pores and blocking of the permeation path anddepletion of the braze material. A preferred method for eliminating thisproblem is to apply a stop-off material such as Nicrobraz® Greenstop-off produced by Wall Colmonoy Corp. (Madison Hts., Mich.) betweenthe braze area and the perforated or porous support. Another method toprevent braze flow to porous components is to machine a channel betweenthe braze area and the perforated or porous support to provide areservoir for excess braze to run off without flowing into theperforated or porous support itself.

Even though the hydrogen separation membrane is described above as athin membrane foil (8), the methods need not be necessarily restrictedto foils. For example, the hydrogen separation membrane can be appliedto the faces of the porous substrates using deposition techniques. Inthese methods, precursors of the palladium or palladium membrane areapplied to the faces of the substrates and are then decomposed to theirmetallic components to yield a defect free membrane film. These thinfilm containing substrates can then be integrated into the device usingsuitable joining techniques such as brazing, welding, and diffusionbonding. A porous ceramic mat can be disposed between the substrate inthe reaction chamber and the membrane surface. A retaining frame canalso be comprised to hold the mat in contact with the substrate toeliminate contact between the membrane surface and the substrate.

The reaction chamber (2) contains a suitable catalyst material togenerate hydrogen from hydrocarbons or non-hydrocarbons such as ammoniaor oxygenates such as alcohol. In the case of hydrocarbons, steamreforming is the preferred route with typical operating conditionsbetween 575 and 650° C. and between 5 and 10 bar. The catalyst can be inthe powder form (45 to 140 mesh) and loaded into mesochannels that maybe machined into the reactor body. The flow dimensions of themesochannels are typically between 0.5 and 2 mm. More preferably thecatalyst material is coated onto substrates such as metal foams ofalloys such as Fecralloy® or Inconel® as supplied by Porvair(Hendersonville, N.C.) with the dimensions of the irregular flowchannels in the foams still being in the mesoscale range of 0.5 to 2 mmrange. The catalyst coated substrate is then inserted into the reactorbody. Preferably a porous pliable material lies between the catalyst andthe membrane foil surface to prevent any damage (scratches, holes etc)to the thin membrane foil. A preferred candidate for a pliable materialis the Interam™ 1101 HT ceramic mat as supplied by 3M Corporation(Minneapolis, Minn.). Example 1, later described, demonstrates purehydrogen production using a reactor sub assembly as shown in FIG. 1 thatcontains a porous metal support in place of the perforated plate tosupport the membrane foil. Example 2, later described, demonstrates purehydrogen production using a reactor sub assembly as shown in FIG. 1 thatcontains a perforated plate as a support for the foil. The results shownin Examples 1 and 2 teach that the sintered porous metal substrate is apreferred support for supporting the hydrogen separation membrane foil.The location of the entry and exit ports in FIG. 1 is shown in exampleonly. The catalyst, palladium and/or any other components in the reactorassembly can be deposited onto the surface using techniques such ascold-spray technique described in PCT/US04/37620 herein incorporated byreference.

FIG. 2 shows a sectional view of reactor sub assembly (20) which is adouble sided variant of reactor subassembly (10).

In reactor sub assembly (20), a membrane assembly consisting of themembrane support sub assembly and the foil (8) is located on both sidesof the reaction chamber (2) containing the catalyst. Hydrogen generatedin the reaction chamber permeates through the membrane foils (8) andsupports (6), flows through the perforations in the support (7), and iscollected in the hydrogen plenum (4) on either side of the reactionchamber (2).

Since the hydrogen permeation rate through the membrane increases withavailable membrane surface area for a given set of operating conditions,this embodiment effectively increases the available surface area forhydrogen permeation by 100% while increasing the unit mass by only 30%when compared to the reactor sub assembly in FIG. 1. Accordingly, thisembodiment allows to increase the hydrogen production rate withoutincreasing the footprint of the basic unit. The location of the entryand exit ports in FIG. 2 is in example only and other variations arepossible.

FIGS. 3A (exploded perspective view) and 3B (compact perspective view)illustrate an exemplary double sided hydrogen separation membraneassembly (30).

In the membrane assembly (30), a membrane support sub assembly includinga sintered support (24) and a housing (26) is integrated with more thanone membrane (22). The housing (26) includes an hydrogen exit port (28).In the membrane assembly (30), the sintered porous support (24) isnested inside a housing (26) and sandwiched between a membrane (22) oneither side.

When a hydrogen containing gas is exposed to the membrane surfaces underappropriate operating conditions, hydrogen permeates through themembrane surfaces, flows through the porous support and out of thehousing through the hydrogen exit port (28). The support (24) acts notonly as a support for the membranes but also serves the purpose of flowchannel for transporting hydrogen from the surface of the membranes tothe exit port (28).

A distinct advantage of this membrane assembly embodiment lies in thefact that both sides of the component are at the same pressure, and thusthe strength of the support is limited only by the compressive yieldstrength of the support which is much higher than the tensile strengthof metals and ceramics. A membrane assembly arranged in this manner ishighly suitable for high pressure applications as the stress on thesupport of the membrane is equalized by the pressure on both sides.

The support (24) is preferably intrinsically porous in nature such asporous sintered metals or porous metal foams. Porous metal substratesare preferred to ceramic substrates because components can be readilyjoined using conventional techniques such as brazing, welding etc. Thehousing, frame and the foil that constitute the membrane assembly may bejoined in a leak tight fashion using techniques such as brazing,welding, diffusion bonding, or other applicable joining techniques.

FIG. 4 shows a reactor sub assembly (40) constituting an exemplaryvariant of reactor sub assembly (20) shown in FIG. 2, which incorporatesthe double sided membrane assembly (30) shown in the sectional views ofFIGS. 3A and 3B.

In the reactor sub assembly (40), a double sided membrane assembly (30)is placed on both sides of the reaction chamber (2) separating thereaction chamber (2) from two plenums (34) which include a tail gasplenum. Accordingly, each of the membrane assemblies (30), comprises afirst membrane (22 a) facing the reaction chamber and a second membrane(22 b) facing the plenum (34).

The hydrogen containing feed or fuel that needs to be reformed entersthe reaction chamber (2) through the entry port (14). Tail gases,including hydrogen and possibly other components such as CO, CH₄, CO₂,are generated in the reaction chamber (2) and permeates the membranesubassembly (30) through the membranes (22 a). Instead of exiting thereaction chamber at the end opposite to that of the entry port (14), thetail gases are routed through the internal reject port (32) and come incontact with by the second set of membrane surfaces (22 b). The hydrogenthat continues to be collected by permeating through the membranes,flows into the porous support (24) and exits through the hydrogen exitport (28). The tail gases rejected by the membranes (22 a) and (22 b),exit through the reject exit ports (36) located in each membraneassembly.

The reactor sub assembly (40) provides an additional increase in purehydrogen production rates with minimal increase in reactor footprintwhen compared to reactor sub assembly (20) shown in FIG. 2.

To prevent any flow restrictions or impediments through the membranesdue to the support material, the porosity of the sintered poroussubstrate should preferably be between 20% and 50%. In addition, thethickness of the support may be increased to allow a larger flow regionthat separates the membranes. Each of the two membrane assemblies (30)in the reactor sub assembly (40) shown in FIG. 4, incorporates fourmembrane foil surfaces, thus increasing the exposed membrane area by400% when compared to the reactor sub assembly shown in FIG. 1, whileincreasing the weight by only 40%.

The reactor sub assemblies shown in FIGS. 1, 2 and 4 can also be used asstandalone hydrogen purifiers as demonstrated by later describedExample 1. The purifiers can be utilized to produce pure hydrogen froman impure hydrogen feed (example 99% or less) for applications such asthe semiconductor industry. In such applications, the catalyst can bereplaced by a porous media that does not contain catalyst coating.

FIG. 5 shows a reactor sub assembly (50) which constitutes an exemplaryplenum-les variant of the reactor sub assembly (10) shown in FIG. 1. Themembrane assembly (55) here consists of a membrane foil (44) supportedon a sintered porous metal support (42) that is inserted into a plate(38). The sintered porous metal support (42) serves the dual purpose ofproviding support for the membrane and of behaving as channel fortransporting hydrogen from the membrane surface to the exit port (48).Additional collection channels (46) may be included in the plate (38).The resulting reactor sub assembly is therefore very compact.

FIG. 6 shows an exemplary variant of plate (38) that contains a recessto receive the porous metal substrate (44), and hydrogen collectionchannels (46) machined on to the surface of the plate facing the porousmetal substrate. The pattern of these channels is shown in example only.

In the reactor sub assembly (50) shown in FIG. 5, hydrogen containingfeed or the fuel that needs to be reformed enters the reaction chamber(2) through the entry port (14). Hydrogen is generated in the reactorchamber, permeates through the membrane foil (44), flows through theporous metal insert (42) and is routed through channels (46) machinedinto the plate (38). Pure hydrogen exits the reactor sub assemblythrough one or both of the exit ports (48). The tail gases rejected bythe membrane exit the reaction chamber through the port (16).

Plenumless variants analogous to the reactor sub-assembly (50) can bederived from of other reactor sub-assemblies, such as reactor assembly(20), (30) and (40) by a person skilled in the art based on the contentof the present disclosure and will not herein described in furtherdetails.

FIG. 7 shows a reactor sub assembly (60) which constitutes a variant ofthe plenum-less reactor sub assembly (50) shown FIG. 5. In the reactorsub assembly (60) a header (52) is located at the hydrogen exit ports(48) of the reactor sub assembly. This header facilitates hydrogenremoval by creating a larger volume for hydrogen collection in closeproximity to the exit ports. In some embodiment the header also allowsremoval of flow impediments.

As known to those skilled in the art, hydrogen separation throughpalladium based membranes is effected at temperatures greater than 350°C. Hydrogen generation via steam reforming or otherwise requirestemperatures in excess of 350° C., preferably around 550 to 650° C.Therefore, heat needs to be provided to the reactor sub assembliesdescribed above. Heat may be provided externally using either aresistance wire or other electrical means (such as in Examples 1 and 2).An alternate preferred embodiment would be to integrate a combustionchamber with the reactor sub assembly to form a membrane reactor. In thedisclosure described here, a hydrogen generator is composed of amembrane reactor with associated fluid lines, such as a air supply, areaction fuel supply and a combustion fuel supply, for transport ofappropriate streams in and out of the membrane reactor.

FIG. 8 illustrates an exemplary membrane reactor (70) which includes areactor sub assembly (10) shown in FIG. 1 integrated with a combustionchamber (62). The reaction chamber (2) in the reactor subassembly andthe combustion chamber (62) are disposed on either side of a separationplate (15). An end plate (17) close the combustion chamber on the sideopposing the separation plate (15). In the membrane reactor (70), thecombustion chamber (62) provides heat to drive hydrogen generation andseparation.

The combustion chamber (62) comprises a combustion chamber substrate andthe reaction chamber (2) comprises a catalyst coated reaction chambersubstrate, formed by the membrane (8). The approximate pore diameter orflow dimension of the substrates can be in the 0.2 to 3.0 mm range.

Combustion fuel and air enters the combustion chamber at the entry port(64) and is converted to CO₂ and H₂O while generating heat. The fuel tothe reaction chamber (examples, fuel and water in the case of steamreforming of hydrocarbons, ammonia in the case of ammonia cracking)enters the reaction chamber (2) through the entry port (14) and reactiontail gases exit through the port (16). The generated hydrogen permeatesthrough the membrane (8) and through the membrane support sub assemblyconsisting of the porous support (7), the perforated plate (6) tosupport (7), and into the plenum (4), and exits the unit through theexit port (18). The tail gases from the combustion chamber or combustionby-product gases exit through the exit port (66).

Combustion is preferably confined to catalytic combustion, whereby, theheat is generated in a flameless fashion. This method is inherently safeand is suitable for a wide range of applications and particularly forfuel cell applications for portable services. The catalyst can be in thepowder form (45 to 140 mesh) and may be loaded into mesochannels thatmay be machined into the reactor body. The flow dimensions of themesochannels are typically between 0.5 and 2 mm. More preferably, thecatalyst material is coated onto substrates such as metal foams ofalloys such as Fecralloy®, Fe CrAlY, austenitic steel or Inconel® assupplied by Porvair (Hendersonville, N.C.) with the dimensions of theirregular flow channels in the foams still being in the 0.5 to 2 mmrange. The catalyst containing substrate is then inserted into thereactor body. In contrast to the reaction chamber, a ceramic mat neednot be placed between the catalyst the surface of the reaction chamberthat is in contact with the combustion chamber.

Catalytic combustion is initiated at a temperature commonly denoted asthe “light-off” temperature for a particular catalyst. For hydrocarbons,this light-off temperature is typically in the 150 to 350° C. range; forexample the light-off temperature for propane over noble metalcontaining catalysts is around 175° C. The catalyst may be heated tothis temperature using ancillary heating methods such as through aresistance wire that is powered by a battery or other electrical source.Alternately, since hydrogen can light-off at room temperature overcertain noble metal containing catalysts, hydrogen stored in a smallhydride canister, in a compressed cylinder, or in a liquefied state canbe used to increase the temperature of the catalyst from roomtemperature to light-off temperature during start-up.

The fuel for combustion can constitute a fraction of the same fuel thatis used as the feed for hydrogen generation. Alternately, an externalfuel or an ancillary fuel may also be supplied. Also, a fuel supplyproviding fuel to both the reaction chamber and the combustion chambercan be provided. Alternatively, a reaction fuel supply can be providedseparate from a combustion fuel supply. More preferably, the reactionchamber tail gases that contain H₂ and combustibles such as CO andhydrocarbons rejected by the membrane that exits through the port (16)in FIG. 8 can be routed into the combustion chamber through the port(64). The reaction chamber tail gases can thus be utilized either as thesole source of heat for the endothermic hydrogen generation reaction oras a supplement to the existing secondary fuel source to improve systemefficiency.

FIG. 9 illustrates an exemplary membrane reactor (80) which includes thereactor sub assembly (20) shown in FIG. 2 integrated with a combustionchamber (62). In the membrane reactor (80) the combustion chamber (62)is located between the two reaction chambers (2 a) and (2 b) in aconfiguration wherein more than one membrane surface is provided forhydrogen separation.

In particular, in this embodiment, a combustion chamber (62) issandwiched between two reaction chambers (2) in a compact manner thatgenerates heat to drive both hydrogen generation and separation with100% more membrane surface area than the membrane reactor (70) shown inFIG. 8. The combustion fuel and air enter through the entry port (64).The tail gases from the combustion chamber exit through an exit port(66).

FIG. 10 illustrates a membrane reactor (90) which is an exemplaryvariant of a membrane reactor (80) shown in FIG. 9, wherein the membraneassemblies constituted by the membrane foil (8) and the support plate(6), are replaced by the membrane assemblies (30) as described in FIGS.3A and 3B. An effect is that the membrane surface area of the membranereactor (90) is increased with respect to the one of the membranereactor (80). In effect, the membrane surface area available forhydrogen separation is twice that of the surface area of the membranereactor (80) shown in FIG. 9, while insuring only a negligible increasein reactor footprint.

FIG. 11 illustrates a membrane reactor (100) which constitutes a variantof the membrane reactor (70) shown in FIG. 8. In the membrane reactor(100) the membrane assembly, constituted by the membrane foil (8) andthe support plate (6), is replaced by several membrane assemblies (30)as shown in FIGS. 3A and 3B, that are arranged in a stacked fashion. Inthis manner, the membrane surface area of the membrane reactor (100) canbe increased with respect to the one of membrane reactor (70) toelegantly provide increased hydrogen generation and production rateswithout increasing the dimensions of the reactor. The number of membraneassemblies can be chosen to satisfy the targeted pure hydrogenproduction rates. The feed and product flow paths should be suitablymanifolded to introduce feed streams and remove product streams from themembrane reactor.

FIG. 12 shows a membrane reactor (110) which constitutes an exemplarypreferred variant of membrane reactor (80) shown in FIG. 9 including aninternal connector (112) located within the reactor between the tworeaction chambers (2 a) and (2 b).

In the membrane reactor (80), the two reaction chambers (2 a) and (2 b)are located on the sides of the combustion chamber (62) and haveseparate entry ports (14) and exit ports (16). Therefore, in themembrane reactor (80) the reaction chambers (2 a) and (2 b) are not influid communication with each other.

In the membrane reactor (110) the internal connector (112) connects thereaction chamber (2 a) and (2 b) through the combustion chamber (62) andfacilitates fluid communication between the two reaction chambers.

In the membrane reactor (110), the internal connector (112) obviates theneed for splitting flows in equal portions that would otherwise berequired while feeding into the reaction chambers of a membrane reactorsuch as membrane reactor (80) as shown in FIG. 9. In addition, theinternal connector (112) also obviates the need for manifolding thereaction chamber tail gas streams that exit the reaction chambers.

In the membrane reactor (110), the reaction chambers (2 a) and (2 b) arein essence “folded” around the combustion chamber to make use of bothhot surfaces of the combustion unit (62) which reduces the exposed hotsurfaces thereby minimizing thermal losses to ambient. The fuel forcombustion may consist of any combustible fuel such as a hydrocarbon(e.g., propane, methane, butane, gasoline, JP-8, diesel fuel, kerosene,biodiesel, etc.) or ammonia and is may be same fuel as fed to thereaction chamber. The primary fuel for combustion can be composed of thetail gas stream from the reaction chambers (2 a) and (2 b) that iseither externally or internally routed to the combustion chamber (62).The fuel and air for combustion enters the combustion chamber throughthe port (64) and exits at the opposite end of the combustion chamber atthe combustion chamber through exit port (66).

The fuel feed from which hydrogen is to be produced is routed into thereaction chamber through the entry port (14). It is preferably preheatedexternally through a separate heating unit or by a heat exchanger priorto be fed into the entry port (14). In the presence of a suitablecatalyst in the reaction chamber, the feed is converted to a hydrogencontaining stream. The hydrogen containing gases flow through thereaction chamber (2 a), and then through the connector (112), and intoto the secondary reaction chamber (2 b), where the un-reacted feed isfurther converted to hydrogen. This connector is part of an otherwisesolid wall that acts as a common interface and separating dividerbetween the reaction chambers and the combustion chamber. The connector(112) may be composed of a tube that is inserted into holes machinedinto the otherwise solid dividing walls and is sealed using techniquescomprising of welding, or brazing. The connector may also be a channelthat is machined or otherwise formed into the reaction chambers duringthe manufacturing/machining process as long as the reactant stream isallowed to internally bypass the combustion chamber without leakage. Thereactor connector (112) could also be plumbed externally between the tworeaction chambers (2 a) and (2 b). Hydrogen is separated through themembrane as the gases flow through the reaction chambers and thereaction chamber tail gases exit the chamber through reject port (16).

In the membrane reactor (110), the sides of the reactor chambers (2 a)and (2 b) that are opposite to the dividing wall between the reactorchambers and the combustion chamber (62), contain the membraneassemblies consisting of the membrane (8) supported on the membranesupport sub assemblies. The membrane which may be in the foil form issupported by the membrane support sub assembly which consists of asupport plate (6) containing perforations (7), or more preferablyconsists of a porous metal plate that is further secured into aperforated metal support to provide additional structural rigidity.

The membrane may also consist of a composite membrane deposited on aporous metal, ceramic, or composite metal/ceramic support through meansof electroless plating, electroplating, sputtering, spin coating,chemical vapor deposition, or other techniques or combinations of thesetechniques. This composite membrane would likewise be further supportedby a perforated or otherwise macro-permeable support structure. In thiscase, the membrane would preferably be isolated from the support metalby a diffusion barrier consisting of an oxidized layer, a ceramic orrefractory metal layer, or barrier composed of other suitable materialto prevent unwanted diffusion from the support into the membrane.

The membrane in the membrane assembly spans the entire length of thereactor chambers and would actively remove hydrogen produced in thereactor chambers. The hydrogen which permeates through the membrane iscollected in the hydrogen plenum (4) and exits through the unit at thetwo ports (18) and may then be used to generate electricity using a PEMfuel cell for example, be routed to a storage container, or be otherwiseutilized.

FIG. 13 shows a membrane reactor (120) which is an exemplary plenumlessvariant of the membrane reactor (110) which includes the membraneassembly is as described in FIG. 5. The membrane reactor is otherwisesimilar to the membrane reactor (110) as described in FIG. 12. The tworeaction chambers (2 a) and (2 b) of the membrane reactor (120) are ininternal fluid communication with each other. Example 4, laterdescribed, shows an example of pure hydrogen production process withrates from a feed 75% H₂/25% N₂ using a hydrogen generator containing amembrane reactor (120) as shown in FIG. 13. Example 5, later described,describes pure hydrogen production rates from ammonia cracking using ahydrogen generator containing a membrane reactor (120) as shown in FIG.13.

The membrane reactor (120) shown in FIG. 13 contains a pure hydrogencollection plenum on the downstream side (low pressure side) of eachmembrane surface. As described in FIG. 5, the reactor sub assembly neednot contain a hydrogen plenum wherein the membrane is supported on aporous metal substrate which is directly supported by a metal supportplate, and whereby the porous metal substrate also provides a connectorfor transporting pure hydrogen from the membrane surface to the exitport of the reaction chamber.

FIG. 14 illustrates an exemplary variant of the membrane reactor (120)including a feed pre-heater. In the variant of the membrane reactor(120) shown in FIG. 14, a winding piece metal tubing (122) is wrappedaround the external surface of the combustion chamber to serve as a feedpre-heater or steam generator. The tubing may be tack welded to insuregood heat transfer. The feed (ammonia in the case of Example 5) flowsthrough this tubing prior to feeding into the reaction chamber and getsheated from ambient temperature to close to reaction temperature. Thispractice insures maximum utilization of the catalyst volume for hydrogenproduction, since preheating is accomplished external to the reactionchamber.

In the examples described above, the membrane foil or a porous substratecontaining a deposited membrane is sealed by “gasketless” joiningtechniques such as brazing. In some services, it may be beneficial toseal the membranes using gaskets that allow for the non-destructiveopening of the reaction chamber for inspection, catalyst replacement,and membrane replacement or for other purposes. The gasket material maybe made of any material that is capable of withstanding up to 600° C. inslightly oxidizing conditions. Candidate materials are graphite such asproduced by Garlock (Palmyra, N.Y.), vermiculite such as produced by TheFlexitallic Group, Inc.(Houston, Tex.), or ceramic such as produced byCotronics, Corp., (Brooklyn, N.Y.). In general, gasketed devices areheavier than gasketless devices due to the need for a flangedconfiguration to house and compress the gaskets.

FIG. 15A (exploded perspective view) FIG. 15 b (compact perspectiveview) and FIG. 16 (compact sectional view) illustrate a membrane reactor(130), incorporating two reaction sub assemblies and one combustionchamber with the reaction chambers in fluid communication with eachother, in which the membrane foil is sealed using gaskets.

The underlying configuration of the membrane reactor is the “folded”membrane reactor configuration described in FIG. 13 incorporating tworeaction chambers and one combustion chamber, with the reaction chambersbeing in fluid communication with each other through a connector (112).Each of the gaskets (132 a) and (132 b) is placed between one of themembrane foils (8 a) and (8 b) and the respective reaction chambers (2a) and (2 b). Each of the sintered porous supports (42 a) (42 b) isdisposed off between one of the foil and one of the respectiveperforated plates (6 a) and (6 b), the latter to provide structuralsupport to the sintered porous support. Hydrogen produced in thereaction chambers (2 a) and (2 b) flows through the porous metalsupports (42 a) and (42 b) and through the perforations (7 a) and (7 b)in the perforated support plates (6 a) and (6 b), and into the hydrogenplenums (4 a) and (4 b). The assembly is held together using bolts (134)that pass through the plenum housings (4 a) and (4 b), perforatedsupport plates (6 a) (6 b), gaskets (132 a) and (132 b), and are securedinto the reactor housings (2 a) and (2 b). Gaskets (132 a) and (132 b)can also be compressed to form a leak tight seal between the membranefoils (8 a) and (8 b) and the hydrogen plenum (4 a) and (4 b) on oneside, and between the membrane foils (8 a) and (8 b) and the hydrogenreactor chamber on the other side. The combustion chamber (62) providesheat for the endothermic hydrogen generation reaction. The two reactionchambers (2 a) and (2 b) are joined to the combustor (62) using joiningmethods such as brazing or welding. Although the fluid entry and exitports are not shown in FIG. 16, they can be suitably located asdescribed elsewhere in this disclosure.

Gaskets (132 a) and (132 b) can be made of a material chosen from agroup consisting of Grafoil, metal reinforced Grafoil, ceramic, andvermiculite. Gaskets (132 a) and (132 b) can also have a thickness in arange of 1.5 mm to 6.5 mm.

Example 6, later described, illustrates pure hydrogen production fromammonia using a hydrogen generator containing the membrane reactordescribed in FIGS. 15A, 15B and 16. As can be seen in Example 6, about 4ppm of ammonia was detected as impurities in the pure hydrogen streamexiting the reactor. This ammonia impurity was easily removed by flowingthe hydrogen stream through a bed of molecular sieve 4A adsorbents(25/35 mesh particles, Grade 514, Grace Davison).

Variants of reactor assemblies having components disposed in a differentconfiguration than the one disclosed in FIGS. 15A, 15B and 16 andwherein the components are sealed through gaskets can also be providedaccording to the present disclosure. As an example, a hydrogen generatorcontaining a gasketed membrane reactor having the underlyingconfiguration of the membrane reactor (70) described in FIG. 8, can beprovided according to the present disclosure.

Example 7, later described, illustrates pure hydrogen production from asynthetic kerosene fuel (ClearLite™, product of Exxon) by steamreforming using this gasketed variants of the membrane reactor (70),that is, one reactor sub assembly integrated with one combustionchamber.

In the description taught in Example 7, the hydrocarbon feed was firsttreated in a feed pre-treatment chamber that was located external to themembrane reactor unit to produce hydrogen containing gases. The catalystcoated substrate located in the feed pre-treatment chamber can bedifferent from a catalyst located in the reactor chamber.

It would be advantageous to integrate a feed pre-treatment chamber withthe membrane reactor to exploit the heat available from the combustionchamber. Furthermore, it would be advantageous to vaporize the waterprior to feeding into the pre-treatment chamber.

FIGS. 17 and 18 describe membrane reactor (140) which constitutes anexemplary membrane reactor, including the reactor subassembly (70)described in FIG. 8 with a water vaporizer and a pre-treatment chamber.

The membrane reactor (140) is identical to that described in FIG. 8, buta pre-treatment chamber (142) is integrated with the combustion chamberto utilize heat generated from the combustion chamber (62) to drive thepre-treatment process. Water enters the membrane reactor at thevaporizer tubing (144) and passes through a coil that is in closecontact with the external surface of the pre-treatment chamber (142).This coil is joined either through brazing or welding to provide themost intimate contact for best thermal conduction. The water passesthrough the coil and enters the pre-treatment chamber at entry port(147). Fuel enters the pre-treatment chamber through the fuel entry port(146). The fuel entry port is shown as being on the side of thevaporizer body but may be located in any manner which provides theinjection of the fuel in close proximity to the entry point of thevaporized water. The pre-treated fuel now containing some hydrogen,flows through exit port (148), and into a pre-treatment chamber-reactionchamber connecting tubing (143). This tubing may be located eitherexternal to the reactor as shown or preferably internal to the reactorin a similar manner to the connector element (112) shown in FIGS. 12,13, and 16. Example 9, later described, demonstrates pure hydrogenproduction from kerosene and Example 10, later described, demonstratespure hydrogen from propane using a hydrogen generator containing themembrane reactor as described in FIG. 18. As described in Example 10,the membrane reactor as described in FIG. 18, permits uninterrupted purehydrogen production even during the “hot-swap” of fuels which involveschanging from one fuel to another while the membrane reactor is hot.Example 11, later described, demonstrates pure hydrogen production fromalcohol-water mixtures using a hydrogen generator containing themembrane reactor as described in FIG. 18.

The integration of a vaporizer and pre-treatment chamber to a membranereactor configuration as shown in FIG. 8 to yield a configuration asshown in FIG. 18 is only exemplary. The same procedure can be practicedin other membrane reactor configurations that may follow a stacked ormodular pure hydrogen producing package. Also the presence of apre-treatment chamber separated from a reaction chamber is notnecessary.

FIG. 19 shows a reactor sub assembly (200) which is an exemplary variantof reactor sub assembly (140) shown in FIG. 18, wherein thepre-treatment chamber is not separated from the reaction chamber.

In the reactor sub assembly (200) a portion of the reaction chambersituated close to the entry port of the reformer chamber can constitutethe pre-treatment chamber. This pre-treatment of portion of the reactionchamber would be differentiated from the rest of the reaction chamber bythe absence of the membrane. In other words, the membrane assemblycontaining the membrane would not extend into the pre-treatment chamberas illustrated in FIG. 19.

In the membrane reactor (190) shown in FIG. 19, the pre-treatmentchamber section (196) is the membrane less portion that is located infront of the reaction chamber (202) that is exposed to the membraneassembly reaction area (202). During the steam reformation ofhydrocarbons for example, water is vaporized by passing through a metaltubing (194) that is in contact with the external surface of thecombustion chamber (62). This metal tubing may be joined either throughbrazing or welding to provide the most intimate contact for best thermalconduction. Water is vaporized in the metal tubing and may be furtherheated beyond the normal boiling point coil and enters the pre-treatmentsection of the reformer chamber (196). Fuel enters the pre-treatmentchamber of the reformer chamber through the port (198). The fuel entryport is shown as being on the side of the vaporizer body but may belocated in any manner which provides close contact between the vaporizedwater and fuel once they enter the pre-treatment chamber. In thepre-treatment chamber the fuel is partially converted to a gaseousmixture containing hydrogen and this gaseous mixture flows into thereaction chamber (202) that contains the membrane. This insures that themembrane surface is exposed to a reducing mixture (due to the presenceof hydrogen) that would prevent the deterioration of the membrane byoxidation. Hydrogen flows through the membrane assembly, gets collectedin the hydrogen plenum (192) and exits through the hydrogen exit port(18). The construction of the membrane assembly in the membrane reactorshown in FIG. 19 is similar to that described in FIG. 18.

The integration of a vaporizer and pre-reformer to a membrane reactorconfiguration shown in FIG. 18 to yield a membrane reactor as shown inFIG. 19 is only exemplary. The same procedure can be practiced on othermembrane reactor configurations that have been described in thisdisclosure to produce a stacked or modular pure hydrogen producingpackage that contains integrated vaporization and pre-reformingcapability.

A critical problem in using hydrogen separation membranes on acommercial scale relates to thermal issues with regards to reliability,lifetime and ability to withstand multiple thermal cycles. As taught inthis disclosure, the membrane can be sealed by gasketing, brazing,welding (electron beam, laser, TIG, or other), diffusion bonding.Thermal cycling between room temperature and 600-650° C. (membranetemperature during reforming) increases the stress on the thin membraneswhich may be in the thin foil form. The introduction of hydrogen createsfurther difficulties because palladium based membranes absorb hydrogenand swell in volume (increases in volume). The palladium foil isparticularly subjected to enormous stresses around the circumference ofthe joint. This is especially prevalent in rigid joints that result fromusing techniques such as brazing and welding (as opposed to gasketing).

In the case of gasketing, the thin foil is sealed by using removablegaskets that are housed in flanged assemblies. All of these gasketmaterials degrade over time (especially in the case of the oxidation ofgraphite when not in an inert environment) and the mechanical joiningcomponents such as bolts and screws experience elevated creep rates athigh temperatures thus further weakening the seal. Thermal cyclingeffects amplify failure rates by inducing fatigue into the mechanicalfasteners such as bolts. Sealing using gaskets allows some slippagearound the gaskets that may contaminate the hydrogen stream.Furthermore, the use of flanges increases the weight of the reactor,which is undesirable for compact portable power systems.

It is possible to combine the flexibility afforded by gaskets with thatof the leak-tight seal and lower weight afforded by permanent joiningtechniques. This hybrid joining technique that seals the foil to thesupport structure can reduce membrane failure and provide a reliableseal between the membrane and support structure.

FIGS. 20A, 20B and 21 show respectively an exploded, a compact and asectional view of a membrane assembly and hydrogen plenum (150) in whichthe gasket is housed in a support frame. A high temperature gasket (158)made of a material such as graphite, ceramic, vermiculite, or otherappropriate material is incorporated at the interface of the membranefoil (156) and a frame (162) is placed on top which secures the foil tothe support. This assembly is then placed on top of the perforated orotherwise porous support (154). The assembly may then be compressedusing a clamp. The areas outside of the gasket can be brazed usingvacuum brazing or other appropriate brazing methods with the brazeapplied to the areas to be joined prior to compressing the gasket inplace. Alternately, the elements of the membrane assembly may be weldedaround the perimeter using appropriate welding techniques taking carenot to damage the foil. After sealing, the clamps are removed and themembrane assembly is integrated into the hydrogen plenum (152) usingbrazing or welding. FIG. 21 shows a section view of the membraneassembly that is integrated with the hydrogen plenum. When exposed to ahydrogen containing gas mixture at appropriate conditions, hydrogenpermeates through the membrane foil (156) and flows through theperforations (166) or porous structure of the membrane support plate(154) and into the hydrogen plenum (152). Hydrogen then exits the plenumthrough the hydrogen exit port (164). The membrane assembly described inFIGS. 20A, 20B and 21 can be integrated with a reaction chamber andcombustion chamber to yield a membrane reactor as described in thisdisclosure.

FIG. 22 shows an exemplary membrane assembly (180) wherein the membranecomponents described elsewhere in the disclosure are replaced by tubularcomponents. An effect of this replacement is that increased hydrogenproduction rates can be achieved with respect to the membrane assembliesincluding non-tubular membrane components. The membrane assembly (180)as shown in FIG. 22, consists of a housing (184) for the tubularmembranes component (182) and comprises of a plate with closed endedcavities (181) for the tubular membranes to be positioned, shown in FIG.23. The generated hydrogen permeates through the surface of the tubesflow into a collection area (186). The tubes are positioned in anopening (183) that is located opposite to (181) and open into acollection header (186) as shown in FIG. 23. The hydrogen exits thehydrogen exit port (188) to the point of use. The tubes may be sealedinto the housing using brazing methods, preferably under vacuum brazingconditions described above.

FIG. 23 shows an exemplary membrane reactor (190) which includes amembrane sub assembly (180) as shown in FIG. 22, integrated with acombustion chamber. Other than differences in the membrane assemblies,this membrane reactor is similar to the membrane reactor shown in FIG.8. The membrane assembly (180) shown in FIG. 22 contains seven tubularelements with a total membrane surface area of 110 cm². A planarmembrane which is sized to fit in the space accommodating the tubeswould possess a surface area of 58 cm². Therefore an almost 2-foldincrease in the surface area can be realized using a membrane assemblyas shown in FIG. 22, which should translate to a 2-fold increase in thehydrogen permeation rate if the membrane thickness are assumed to the bethe same.

The extremities of the tubular membrane components could be composed ofmaterials not permeable to hydrogen to allow for sealing of the tubeswith the membrane assembly. Accordingly, the tubular membrane componentscan be dead-ended or closed ended at one end of the component.

In the examples taught below the hydrogen separation membraneconstitutes a 25 micron thick Pd/Ag foil. It is claimed here thatmembrane foil of different thicknesses can also be incorporated in thesame manner as that followed for the 25 micron thick foil.

The membrane reactors, the reactor sub-assemblies and the membraneassemblies herein described can be included in a hydrogen generator, andin particular in an ammonia based or hydrocarbon based hydrogen reactor.

FIG. 24 shows an exemplary ammonia based hydrogen generator includingthe membrane reactor of FIG. 8. The membrane reactor (70) is connectedto a fuel supply (204) through a reaction fuel supply line (205) and toa combustion fuel supply (207) through a combustion supply line (211).The membrane reactor (70) is also connected to an air supply (203)through a air supply line (206). The hydrogen generator also includes acombustion byproduct line (208) and a tail gases supply line (209).

FIG. 25 shows an exemplary hydrocarbon based hydrogen generatorincluding the membrane reactor of FIG. 8. In the hydrocarbon basedhydrogen generator, the membrane reactor (70) is connected to a fuelsupply (204) through a reaction fuel supply line (205) and to acombustion fuel supply (207) through a combustion supply line (211). Themembrane reactor (70) is also connected to an air supply (203) through aair supply line (206). The membrane based hydrogen generator alsoincludes a combustion byproduct line (208) and a tail gases supply line(209). A water supply (212) connected to the membrane reactor (70)through a water supply line (213) is also included.

The following examples are provided to describe the invention in furtherdetail. These examples, which set forth a specific mode presentlycontemplated for carrying out the disclosure, are intended to illustrateand not to limit the invention.

EXAMPLES Example 1 Hydrogen Flux Through a Reformer Sub Assembly inwhich the Membrane is Supported on a Sintered Porous Metal Substrate

A gas mixture consisting of hydrogen and nitrogen in the nominalvolumetric ratio of 75% H₂ and 25% N₂ and at a nominal flow rate of 1500sccm was fed into a reaction chamber as shown in FIG. 1 after heatingthe chamber to about 450° C. The reaction sub assembly was constructedof SS 304. The membrane consisted of a Pd/Ag foil of nominal composition75% Pd/25% Ag and had a surface area of 23 cm².

The membrane foil, 25 microns in nominal thickness, was supported on asintered porous stainless steel 316L substrate that possessed a nominalporosity of 41% (Mott Corp). The reactor sub assembly was placed in aWatlow electrical furnace which allowed for increasing the temperatureof the furnace using a suitable temperature controller (Omega). Thereaction chamber contained a 40 ppi FeCrAlY metal foam substrate toprovide uniform flow and heat distribution.

The gas mixture was preheated by flowing through a ⅛ in. OD SS 316tubing coil that was also situated in the Watlow furnace. The hydrogenflux (sccm/cm²) through the reactor sub assembly was measured, while thereactor sub assembly was operating at a nominal temperature of 600° C.and nominal pressure of 5.8 bar. The pressure on the permeate side ofthe membrane was therefore maintained at atmospheric pressure. Stabilityof the flux was measured.

The results, reported on FIG. 26, show a stable hydrogen flux observedduring the testing period that spanned over 50 hours of continuousoperation.

Example 2 Hydrogen Flux Through a Reactor Sub Assembly in which theMembrane was Supported on a Solid Plate Containing Perforations

The test as described in Example 1 was repeated using reactor subassemblies that were identical to that used in Example 1, except for thefact that the membrane foil was supported on a solid SS 304 plate thatcontained small evenly spaced holes 1/32″ diameter with a total exposedsurface area of 0.23 in². In particular, hydrogen flux (sccm/cm²) waspassed at 600° C. and at a nominal pressure of 5.8 bar through twoidentically construed Units 1 and 2, at various temperature cycles. Eachtemperature cycle was between ambient temperature and 600° C.

The pressure on the permeate side of the membrane was maintained atatmospheric pressure. The results reported in FIG. 27 show anapproximately 30% decrease in hydrogen flux was observed with time. Themembrane was found to be very stable to thermal cycling between ambienttemperature and 600° C., as no decrease in the purity of hydrogen wasobserved. The nominal hydrogen purity as assessed using a Shimadzu GC 17gas chromatograph was found to be >99.99% (impurities if any were belowthe detection limits of the gas chromatography. The decrease in flux isattributed to the gradual creep of the membrane foil into the holes ofthe support at temperature, which results in a decrease in the effectivesurface area of the membrane that is available for hydrogen transport.The test was repeated for an identical unit, Unit 2, and both unitsexhibited the same behavior of decreasing flux when subjected to theevaluation described above (see FIG. 27).

Example 3 Hydrogen Flux Through a Reactor Sub Assembly in which theMembrane was Supported on a Sintered Porous Substrate

The substrate also behaved as a flow channel for transport of hydrogento the exit ports of the device.

A gas mixture consisting of hydrogen and nitrogen in the nominalvolumetric ratio of 75% H₂ and 25% N₂ and at a nominal flow rate of 3600sccm was fed the reactor sub assembly as shown in FIG. 5 after heatingthe reactor to about 450° C. The reactor sub assembly was constructed of304L stainless steel. The membrane consisted of a Pd/Ag foil of nominalcomposition 75% Pd/25% Ag and had a surface area of 55 cm². The membranefoil was supported on a sintered porous 316 stainless steel substratethat possessed a nominal porosity of 41% (Mott Corp). The membranereactor was placed in a Watlow electrical furnace which allowed forincreasing the temperature of the furnace using a suitable temperaturecontroller (Omega). The reaction chamber contained a 40 ppi Inconel® 625metal foam substrate to provide uniform flow and heat distribution.

The gas mixture was preheated by flowing through a ⅛ in. OD SS 316tubing coil that was also located in the Watlow furnace, and introducedinto the reactor sub assembly while operating at a nominal temperatureof 600° C. to 625° C. and nominal pressure of 5.8 bar. Four thermalcycles between ambient temperature 625° C. was performed. The pressureon the permeate side of the membrane was maintained at atmosphericpressure. As shown in FIG. 28 the nominal pure hydrogen production ratewas measured to be 1500 sccm (nominal flux of 27 sccm/cm²), and wasunaffected by thermal cycling between ambient temperature and 625° C.The nominal hydrogen purity as assessed using a Shimadzu GC 17 gaschromatograph was found to be >99.99% (impurities if any were below thedetection limits of the gas chromatograph). The membrane sealing methodwas found to be very stable to thermal cycling both pure hydrogenproduction rates and hydrogen purity remain stable with time.

Example 4 Pure Hydrogen Production from a H2/N2 Feed Using a HydrogenGenerator Containing a Membrane Reactor as Shown in FIGS. 13 and 14

A gas mixture consisting of hydrogen and nitrogen in the nominalvolumetric ratio of 75% H₂ and 25% N₂ and at a nominal flow rate of 3800sccm was fed into a membrane reactor as shown in FIGS. 13 and 14 afterheating the reactor to about 550° C. The membrane reactor wasconstructed of 304L stainless steel and contained a combustion chamberthat was sandwiched between the two reactor chambers that were in fluidcommunication with each other. Each reaction chamber contained amembrane that consisted of a Pd/Ag foil (Johnson Matthey) of nominalcomposition 75% Pd/25% Ag and had a surface area of 55 cm². The membranefoil was supported on a sintered porous SS 316 substrate that possesseda nominal porosity of 41% (Mott Corp). Each reactor chamber contained a40 ppi Inconel® 625 metal foam substrate. The metal foam substrate wascoated with a suitable catalyst material that was effective forproducing hydrogen from ammonia by cracking.

The combustion chamber contained a 40 ppi FeCrAlY metal foam substratethat was coated with a suitable combustion catalyst. A ⅜ inch ODInconel® 600 tubing was wrapped around and tack welded to the combustionchamber as shown in FIG. 14 to provide a degree of pre-heat to the feedstream prior to entry into the reaction chamber. Combustion wasinitiated by room temperature light-off using hydrogen/air mixtures, andwhen the catalyst temperature reached about 200° C., the hydrogen fuelwas replaced with propane. Catalytic and flameless combustion of propanewas carried out in such a manner that the catalyst temperatures in thereaction chambers were between 575 to 625° C. The membrane reactor wasinsulated using Dynaguard™ microporous silica insulation as sold byThermodyne Corporation (Elkhart, Ind.)

Pure hydrogen production rates of 2400 to 2700 sccm were measured duringthis test at a nominal reactor chamber pressure of 5.8 bar. The nominalhydrogen purity as assessed using a Shimadzu GC 17 gas chromatograph wasfound to be >99.99% (impurities if any were below the detection limitsof the gas chromatograph). The tail gas stream exiting the reactionchamber consisted of 30% H₂ and 70% N₂ by volume.

Example 5 Pure Hydrogen Production from Anhydrous Ammonia Using aHydrogen Generator Containing a Membrane Reactor as Shown in FIGS. 13and 14

After demonstrating pure hydrogen production from a H₂/N₂ containingfeed as described in Example 4, the H₂/N₂ feed mixture was replaced byanhydrous ammonia. The flow rates of ammonia feed, membrane reject andpure hydrogen during the production of pure hydrogen from ammonia weremeasured as a function of test time. The results are reported on FIG.29.

As shown in FIG. 29, pure hydrogen at flow rates of 2000 sccm wasproduced in a very stable fashion. The nominal hydrogen purity asassessed using a Shimadzu GC 17 gas chromatograph was found tobe >99.99% (impurities if any were below the detection limits of the gaschromatograph).

Now the reactor tail gases containing hydrogen and nitrogen and traceammonia (<4000 ppm ammonia) can be routed back to the combustion chamberto supply heat to the reactor chamber. This action would reduce theamount of an external fuel such as propane that needs to be fed into thecombustion chamber. In fact, it is quite possible to generate a tail gasstream whose heat content is equivalent to a large fraction or even theentire heat requirement of the hydrogen generation process by changingor “tuning” the flow rate of the ammonia feed.

FIG. 30 shows the heat content of the membrane reject stream based onlower heating value during the pure hydrogen production process.Comparing FIGS. 29 and 30, it becomes evident that a tail gas streamwith a heat content of about 180 W can be generated while maintaining aconstant pure hydrogen production of 2000 sccm. Routing such a tail gasstream back into the combustion chamber resulted in an overall thermalefficiency of 60%, where thermal efficiency is defined as the ratio ofthe lower heating value of pure hydrogen to that of feed streams to bothreaction chamber and combustion chamber.

Example 6 Pure Hydrogen Production from Anhydrous Ammonia Using aHydrogen Generator Containing a Membrane Reactor as Shown in FIGS. 15A,15B and 16

Anhydrous ammonia at flow rates of 500 sccm to 1200 sccm was fed into amembrane reactor as shown in FIG. 17 after heating the reactor to about575° C. The membrane reactor was constructed of 304L stainless steel andcontained a combustion chamber that was sandwiched between the tworeaction chambers that were in fluid communication with each other. Eachreaction chamber contained a membrane that consisted of a Pd/Ag foil(Johnson Matthey) of nominal composition 75% Pd/25% Ag and had a surfacearea of 90 cm². The nominal thickness of the membrane foil was 25microns. The membrane foil was supported on a sintered porous 316stainless steel substrate that possessed a nominal porosity of 41% (MottCorp). Each reaction chamber contained a 40 ppi Inconel® 625 metal foamsubstrate of that was coated with a suitable catalyst. The metal foamsubstrate was coated with a suitable catalyst material that waseffective for producing hydrogen from ammonia by cracking.

The combustion chamber contained a 40 ppi FeCrAlY metal foam substratethat was coated with a suitable combustion catalyst. Combustion wasinitiated by first heating the leading edge of the catalyst using aNichrome resistance wire that was in contact with the leading edge ofthe catalyst. When the temperature of the leading edge of the catalystreached around 200° C., the charge to the resistance wire was stoppedand a mixture of propane and air was fed to the combustion chamber toproduce heat by catalytic combustion.

Alternately, room temperature light-off of the catalyst was accomplishedusing hydrogen/air mixtures, and when the catalyst temperature reachedabout 200° C., the hydrogen fuel was replaced with propane. Catalyticand flameless combustion of propane was carried out in such a mannerthat the catalyst temperatures in the reaction chambers were between 575to 625° C. The membrane reactor was insulated using the Dynaguard™microporous silica insulation as sold by Thermodyne Corporation(Elkhart, Ind.).

Pure hydrogen production rates of 1500 sccm were measured during thistest at a nominal reaction chamber pressure of 5.8 bar as shown in FIG.31. The nominal hydrogen purity as assessed using a Shimadzu GC 17 gaschromatograph was found to be 99.7%. The impurities in the hydrogenstream consisted of minor levels of N2 (2000 ppm), CO (100 ppm), CH4(150 ppm) and CO2 (200 ppm) that are believed to originate either fromoutgassing of the graphite gaskets or seepage around the gaskets. Inaddition, trace levels of ammonia of nominal concentration of 4 ppm(measured using Drager tubes) was present in the hydrogen stream. Thisammonia impurity was easily removed by flowing the hydrogen streamthrough a bed of molecular sieve 4A adsorbents (25/35 mesh particles,Grade 514, Grace Davison).

The tail gas stream exiting the reaction chamber consisted of 22 to 28%H₂, 72 to 77% N₂ by volume and 300 to 1000 ppm ammonia. This tail gasstream was routed back into the combustion chamber to supply heat to thereaction chambers. Routing such a tail stream back into the combustionchamber resulted in an overall thermal efficiency of 63%, where thermalefficiency is defined as the ratio of the lower heating value of purehydrogen to that of feed streams to both reaction chamber and combustionchamber.

Example 7 Pure Hydrogen Production from Synthetic Kerosene in a HydrogenGenerator Containing a Membrane Reactor as Shown in FIG. 8

Synthetic kerosene fuel flowing at a nominal feed rate of 0.16 ml/minwas contacted with distilled water flowing at a nominal feed rate of0.55 ml/min and fed into a pre-treatment chamber of a membrane reactoras shown in FIG. 8. The pre-treatment chamber in this example containeda 40 ppi FeCrAlY metal foam substrate that was coated with a suitablecatalyst. The pre-treatment chamber was heated by an electrical heatingtape and the pre-treatment chamber was maintained at 550 to 580° C. and5.8 bar. The pre-treatment chamber was used to convert the kerosene fuelto a mixture containing hydrogen along with light-hydrocarbons andcarbon oxides.

The hot hydrogen containing gas stream was then fed into the reactionchamber of the membrane reactor whose configuration is as shown in FIG.8. The hydrogen membrane in the reactor comprised of a 75% Pd/25% Agfoil (Johnson Matthey) with a nominal thickness of 25 microns andsurface area of 45 cm². The membrane foil was supported on a sinteredporous 316 stainless steel substrate that possessed a nominal porosityof 41% (Mott Corp).

The reaction chamber and combustion chambers each contained a 40 ppiFeCrAlY metal foam substrate that was coated with suitable catalysts.While operating at a nominal reaction temperature of 610° C. and 5.8bar, pure hydrogen was produced at nominal flow rates of 300 sccm forover 1000 h as shown in FIG. 32.

Combustion was initiated by room temperature light-off usinghydrogen/air mixtures, and when the catalyst temperature reached about200° C., the hydrogen fuel was replaced with propane.

Catalytic and flameless combustion of propane was carried out in such amanner that the catalyst temperatures in the reactor chambers werebetween 575 to 625° C. The pure hydrogen exiting the reactor (beforemethanizer) contained trace levels of CO, CO₂ and CH₄ as impurities asshown in Table I.

TABLE I Purity of hydrogen permeate. TOS CH4 CO2 CO H2 purity Sample (h)(ppm) (ppm) (ppm) (%) Before 980 285 271 206 99.92 methanizer After 981820 51 n.d 99.91 methanizer

The hydrogen product composition was assessed using a pulsed heliumionization detector and a flame ionization detector.

When the hydrogen stream was passed through a bed of methanationcatalyst (T-4308 catalyst; Süd Chemie) maintained at 175° C. and at anominal space velocity of 2000 h⁻¹, all of the CO and a large fractionof the CO₂ were converted to CH₄ resulting in a hydrogen stream of99.91% purity that was suitable for PEM fuel cell applications. Thehydrocarbon conversion calculated as C_(CO+CO2)/C_(products) was 78%with the carbon balance being within 10%.

The nominal molar composition of the reactor tail gas stream was 48.4%H₂, 3.7% CO, 11.7% CH₄ and 36.2% CO₂ on a dry basis. This tail gasstream which had a nominal heating value of 55 to 60 W was routed backto the combustor to provide heat to drive the reforming reaction.

Accordingly, the pure hydrogen stream contained impurities such as CH₄,CO₂ and CO. These impurities can be removed as required by using asuitable hydrogen polishing step. For example, the presence of CO in thehydrogen stream that is fed to a PEM fuel cell can result in adeterioration of fuel cell performance. As shown in Table I, CO waseliminated by flowing the hydrogen gas stream exiting the reactorthrough a methanation catalyst bed (example, T-4308 catalyst supplied bySüd Chemie) that was situated close to the reactor outlet. After a timeon stream (TOS) of about 1010 h, the synthetic kerosene feed was cut-offand was replaced by propane.

The following Example 8 shows pure hydrogen production from propaneusing the same hydrogen generator and exemplifies multi-fuel reforming;that is, hydrogen production from different fuels in a single membranereactor unit.

Example 8 Pure Hydrogen Production from Propane in a Hydrogen GeneratorContaining a Membrane Reactor as Shown in FIG. 8

After demonstrating pure hydrogen production from kerosene for about1010 h as described in Example 7, the kerosene feed was cut-off and wasreplaced by propane. Results of the measurements performed are reportedin FIG. 33.

Propane flowing at a nominal flow rate of 100 sccm was contacted withdistilled water flowing at a nominal feed rate of 0.7 ml/min and fedinto a pre-treatment chamber and then into the reaction chamber in thesame manner as described in Example 7. While operating at a the samenominal reaction temperature of 610° C. and 5.8 bar, pure hydrogen wasproduced at nominal flow rates of 350 sccm as shown in FIG. 31demonstrating multi-fuel reforming capabilities using the membranereactor shown in FIG. 8. The hydrocarbon conversion calculated asC_(CO+CO2)/C_(products) was 70% with the carbon balance being within10%. The nominal molar composition of the membrane reject stream was49.7% H₂, 4.2% CO, 14.4% CH₄ and 31.7% CO₂ on a dry basis. This membranereject stream which had a nominal heating value of 106 to 110 W could berouted back to the combustor to provide heat to drive the reformingreaction.

Example 9 Pure Hydrogen Production from Kerosene in Membrane Reactorthat Contains an Integrated Vaporizer and Pre-Treatment Chamber as Shownin FIGS. 17 and 18

Water flowing at a nominal flow rate of 0.68 ml/min was vaporized tosteam in a tubing that was welded to the skin of the pre-treatmentchamber and was contacted with synthetic kerosene fuel flowing at anominal feed rate of 0.22 ml/min in the pre-treatment chamber. Thepre-treatment chamber in this example contained a 40 ppi FeCrAlY metalfoam substrate that was coated with a suitable catalyst. Thepre-treatment chamber was integrated with the combustion chamber and washeated by heat exchange with the combustion chamber. Feed pre-heatingand pre-reformation was realized at an average temperature of 555° C.and at 5.8 bar. The hot pre-reformed stream was then fed into thereaction chamber of the membrane reactor whose configuration is as shownin FIGS. 17 and 18. The hydrogen membrane in the reactor comprised of a75% Pd/25% Ag foil (Johnson Matthey) with a nominal thickness of 25microns and surface area of 45 cm². The membrane foil was supported on asintered porous 316 stainless steel substrate that possessed a nominalporosity of 41% (Mott Corp). The reaction chamber and combustionchambers each contained a 40 ppi FeCrAlY metal foam substrate that wascoated with suitable catalysts. While operating at a nominal reactiontemperature of 610° C. and 5.8 bar, pure hydrogen was produced atnominal flow rates of 460 to 470 sccm as shown in FIG. 34.

Combustion was initiated by room temperature light-off usinghydrogen/air mixtures, and when the catalyst temperature reached about200° C., the hydrogen fuel was replaced with propane.

TABLE II Purity of hydrogen permeate. TOS (h) CH₄ (ppm) CO₂ (ppm) CO(ppm) H₂ purity (%) 42 3.58 9.98 2.71 99.998 113 5.99 22.31 3.06 99.996187 9.28 47.83 3.7 99.994

The hydrocarbon conversion calculated as C_(CO+CO2)/C_(products) was 73%with the carbon balance being within 5%.

Catalytic and flameless combustion of propane was carried out in such amanner that the catalyst temperatures in the chambers were between 575to 630° C. The purity of hydrogen exiting the reactor was assessed to be99.998% and contained trace levels of CO, CO₂ and CH₄ as impurities asshown in Table II. The hydrogen product composition was assessed using apulsed helium ionization detector and a flame ionization detector. Thenominal molar composition of the tail gas stream was 38.33% H₂, 3.74%CO, 16.98% CH₄ and 40.95% CO₂ on a dry basis. This tail gas stream whichhad a nominal heating value of 84 W was routed back to the combustor toprovide heat to drive the reforming reaction.

Example 10 Pure Hydrogen Production During “Hot-Swapping” of Fuels fromKerosene to Propane in a Membrane Reactor that Contains an IntegratedVaporizer and Pre-Treatment Chamber as Shown in FIGS. 17 and 18

As a continuation of Example 9, kerosene fuel was replaced with propaneat about 210 h into the test without changing other operatingparameters. That is, the fuels were replaced during a “hot swap”, whichis a replacement of the hydrogen generating fuel when the generator isin a steady state. The target was to maintain hydrogen production ratesat the same level as that measured when kerosene was used as the fuel.Water flowing at a nominal flow rate of 0.8 ml/min was vaporized andcontacted with propane flowing at a nominal flow rate of 200 sccm. Asshown in FIG. 35, this target was realized as hydrogen production ratesremained fairly flat in spite of the fuel swap.

Hydrogen permeate samples were collected and sent analyzed at thelaboratories of Matheson Trigas. As shown in Table III, hydrogen puritywas about 99.99%. The hydrogen product composition was assessed using apulsed helium ionization detector and a flame ionization detector. Atthese purity levels, the hydrogen product gas can be directly fed to aPEM fuel cell.

TABLE III Purity of hydrogen permeate after the swap from kerosene topropane TOS (h) CH₄ (ppm) CO₂ (ppm) CO (ppm) H₂ purity (%) 279 15.0530.23 5.72 99.995 354 26.26 106.04 12.14 99.986

The hydrocarbon conversion calculated as C_(CO+CO2)/C_(products) was58%. The nominal molar composition of the tail gas stream was 42.19% H₂,2.64% CO, 24.82% CH₄ and 30.35% CO₂ on a dry basis.

Example 11 Pure Hydrogen Production from Alcohol-Water Mixtures in aMembrane Reactor that Contains an Integrated Vaporizer and Pre-treatmentChamber as Shown in FIGS. 17 and 18

Alcohol-water mixtures (alcohol=ethanol, methanol) flowing at a nominalflow rate of 1.0 to 1.5 ml/min was fed to the pre-treatment chamber. Thepre-treatment chamber in this example contained a 40 ppi FeCrAlY metalfoam substrate that was coated with a suitable catalyst. Thepre-treatment chamber was integrated with the combustion chamber and washeated by heat exchange with the combustion chamber. Feed pre-heatingand pre-reformation was realized at an average temperature of 555° C.and at 5.8 bar. The hot pre-reformed stream was then fed into thereaction chamber of the membrane reactor whose configuration is as shownin FIGS. 17 and 18. The hydrogen membrane in the reactor comprised of a75% Pd/25% Ag foil (Johnson Matthey) with a nominal thickness of 25microns and surface area of 45 cm². The membrane foil was supported on asintered porous 316 stainless steel substrate that possessed a nominalporosity of 41% (Mott Corp). The reaction chamber and combustionchambers each contained a 40 ppi FeCrAlY metal foam substrate that wascoated with suitable catalysts. While operating at a nominal reactiontemperature of 625° C. and 5.8 bar, pure hydrogen was produced atnominal flow rates of about 400 sccm as summarized in Table IV.

TABLE IV Pure Hydrogen Production from Alcohol-Water Mixtures Tail gasSteam: Feed rate Pure H₂ X_(HC) composition Feed Carbon (ml/min) rate(sccm) (%) (dry, %) Ethanol- 3.2 1.52 389 66.1 H₂: 48.0%; Water CO =2.9%; CH₄ = 17.7%; CO₂ = 31.4% Methanol- 2.0 1.08 390 68.4 H₂: 40.8%;water CO = 5.9%; CH₄ = 18.9%; CO₂ = 34.4%

In Table IV, the hydrocarbon conversion (X_(HC)) was calculated as

C_(CO+CO2)/C_(products)

While methods to incorporate palladium based hydrogen separation foilsin pure hydrogen producing devices are described in this disclosure, theprocedures should also be applicable to membranes that have beendeposited on porous substrates, preferably porous metal substrates.

In summary, a hydrogen generator comprising a hydrogen membrane reactor,a fuel supply, a reaction fuel supply line, an air supply, an air supplyline, a combustion fuel supply line, a tail gas supply line, acombustion by-product line for transporting combustion by-products fromthe combustion chamber, and a reaction product line. A membrane assemblyto be joined to a reactor chamber of a hydrogen generator, whichcomprises a membrane; and a membrane support comprising a sinteredporous metal. A reactor assembly comprising a reaction chambercontaining a porous metal substrate, two membrane assemblies, a fuelsupply, a reaction fuel supply line, and a tail gas supply line and areaction product line. Methods associated with the hydrogen generator,membrane assembly and reactor assembly.

The present disclosure has been explained with reference to specificembodiments. Other embodiments will be apparent to those of ordinaryskill in the art in view of the foregoing description. The scope ofprotection of the present disclosure is defined by the appended claims.

1. A method to generate hydrogen from a reaction fuel, the methodcomprising: providing a hydrogen membrane reactor having a combustionchamber centrally disposed in fluid connection with and in heat exchangerelationship between a pair of reaction chambers wherein the reactionchambers each communicate with a membrane assembly on either side of thecentrally disposed combustion chamber, each membrane assembly having atleast a first and second membrane and a porous membrane support, whereinthe first membrane is positioned on a first surface of the membranesupport and the second membrane is positioned on a second surface of themembrane support; transporting a reaction fuel to each reaction chamberthrough a first supply line; transporting air to the combustion chamberthrough an air supply line; transporting combustion fuel to thecombustion chamber through a combustion fuel supply line; reacting thecombustion fuel in the combustion chamber to provide heat and combustionby-products; reacting the reaction fuel with water in the reactionchamber to produce hydrogen and tail gases; and removing the hydrogenfrom the reaction chamber through the membrane supports of the membraneassemblies via a reaction product line.
 2. A method to generate hydrogenfrom a first reaction fuel, the method comprising: providing a membraneassembly to be joined to a reaction chamber of a hydrogen generatorhaving a hydrogen plenum to form a leak tight reactor sub-assembly oneach side of a central combustion chamber, wherein each of the membraneassemblies comprises a first and a second membrane; and a membranesupport, wherein the first membrane is positioned on a first surface ofthe membrane support, the second membrane is positioned on a secondsurface of the membrane support, and wherein the membrane support isconnected to the hydrogen plenum; reacting the first reaction fuel inthe reactor chambers to provide a reaction product comprising hydrogenand tail gases; and separating the hydrogen from the tail gases in thereaction product through the membrane assemblies.
 3. The method of claim2, further comprising: replacing the first reaction fuel in the reactorchamber with a second reaction fuel, whereby replacing the firstreaction fuel with the second reaction fuel results in an uninterruptedhydrogen production.
 4. A method to generate hydrogen from a reactionfuel comprising: providing a pair of membrane assemblies on oppositesides of a generally elongated reaction chamber of a hydrogen generatorhaving a hydrogen plenum, wherein each of the membrane assembliescomprises a first membrane, a second membrane; and a membrane supportstructure therebetween having a plurality of spaces therein, and whereinthe spaces within the membrane support are connected to the hydrogenplenum; reacting the reaction fuel in the reactor chamber to provide areaction product comprising hydrogen and tail gases; separating thehydrogen from the tail gases in the reaction product through themembrane assemblies; and routing the tail gases from the reactionproduct to a combustion chamber in thermal communication with thereaction chamber.
 5. The method of claim 2 wherein said fuel is anon-alcohol fuel.
 6. The method of claim 5 wherein said reacting thefirst reaction fuel is carried out in an operating temperature range offrom about 575 C to about 650 C.
 7. The method of claim 1 furthercomprising routing the tail gases into the combustion chamber.
 8. Themethod of claim 5 further comprising routing the tail gases into thecombustion chamber.
 9. The method of claim 4 wherein said fuel is anon-alcohol fuel.
 10. The method of claim 7 wherein said fuel is anon-alcohol fuel.